Stretchable fabric and method of making same



STRETCHABLL AND METHOD 1 OF MAKING-SAME Reinhold F. SmewegScranton, Pm,r to Grave Silk Company; Scranton, Pa., a corporation of Pennsylyania N0ApplicnflonDe comber 31, 1954,

Serial No- 479, 3

n Claim (CL 2872) andtben thevfitament, are subjected to; setting0981111095 at correlated temperature and timeconditions, they therebyattain the capacity of returning toward the shape existent during thesetting operation, in event of later mechanical twisting or untwisting,for example. Snch'yarns can be referred to as Comprised of stretchedmicrocrystalline polymers. When it is desired to increasethestretchability of a fabric made from multifil yarn, it has beenproposed to set them in twisted form, so that the fabric is thuscomposed of individual. knitted courses, wefts or warps, which havecurls or twists in the filaments. In knitted fabrics there is apermissive stretchability in theloops formed in the knitting, and if amonofil 0r rmrltifil Vq'rn 1's mcmimmn .1: 1 1

versely upontthe setting temperature, other conditions i being the same:torexampl'e the "dead condition may occur at 14 turn unt'wisting (36turns residual) atteritreatment at 170 degrees E, or at 12' turnsuntwisting (38 turns residual) at 200 degrees F.

The behavior of a synthetic yarn is largely determined by its history.Its dispositionupon heating, above room temperaturfl, wncn witloullcxlcmal strut, is In harm the shape 0! relative positron of e partsexistent during. the last prior setting operation: and it may developinternal stresses when detained against free return or relativeposition. operation can only be totally dissipated by a tratment whichis more rigorous than the setting itself. Fol-- example, a yam which hasbeen twisted and set at 200 degrees F. in hot water undergoes a changeof shape or relative positioning which is not completely eliminated by alater immersion in water at such temperature; and in practice some ofthe imposed twist will not be dissipated by treatment at 212 degrees F.

7 It hastbeen found that a yam having a pre-set behavior imposed; atr arelatively? high temperature, which is then t given a right-hand twistof 50 turns per inch and then set,

to such shape In general, the effect of a setting twist is right or lefthand. When an original multifill yarn of denier (7 filaments of about 3denier each) is pre-set for 20 minutes in steam at lbs. pressure, andthen twisted 51 turns and twist-set at 200 degrees in humid air, theliveliness required removal of about 14 turns per inch: that is, moreturns were removed than with a monofil of 20 denier. The product knittedsatisfactorily as an essentially dead yarn. The fabric was treated inboiling water and developed liveliness in the yarn and a satisfactorystretch in the fabric.

Another example of multifil practice with 70 denier (34 filament) yarn,was to pre-set as before in steam at 25 lbs., then twist 65 turns perinch, and twist-set at 180480. The yarn was essentially dead when 24turns were removed, and was knitted. Upon treatment with 212 degreessteam, the yarn exhibited liveliness of 33 turns per inch throughset-release.

A further example with 70 denier (34 filament) multifil yarn was topre-set as before, then twist 103 turns per inch, and twist-set at180-180. The yarn was essentially dead when 33 turns were removed, andwas knitted. Upon treatment with 212 degrees steam, the yarn exhibitedliveliness of 49 turns per inch, and the fabric had a crepe effect.

The amount of original twisting desirable for a given case depends uponthe size of the filament, and the purpose of use. It must be sufiicientto permit the untwisting, after setting, so that the yarn is non-livelyat knitting, and to have a potential efiect available upon set-release,to produce the desired liveliness of the yarn in the fabric. Withfilaments below 10 denier, e. g. at l or 2 denier, the twisting effector liveliness in the fabric yarn may obviously be correspondinglyhigher: while at 20 and denier, significant effects in wide gauge knitfabrics for example can be obtained with twists in the yarn of thefabric of less than 10 turns per inch, and even lower twists for greaterdiameters.

The removal of the liveliness from the twist-set yarn need not beaccomplished upon the individual yarn. For example, two monofil ormultifil yarns can be pre-set, twisted and twist-set, for example withboth yarns having a left twist of 51 turns per'inch. The two ends,without mechanical untwisting to remove the liveliness, can be pliedtogether with, say, 8 turns of right-twist for 15 denier yarn: thebifilar product is then essentially yarn thus treated will not untwistcompletely when left free to adjust itself, but will have stored withinit a condition of potential or residual untwisting ability although thisis not exhibited by physical tendency to untwist further; and since itinvolves a second setting, subsequent to the historical treatment whichpre-sets the filament or subsequent to the preferred pre-setting forstabilizing various yarns to a condition of like prior history of heattreatment.

The treatment .of the yarn or fabric therefrom, by which such residualor potential twisting ability of the yarn is availed of for inducingliveliness therein, can be referred to as a releasing or set-releasingoperation, since it causes residual'or potential stress, resulting fromthe original twisting of the pre-set yarn, to become effective byrelease of the effect of the twist-setting.

Characteristic of {this invention are the preparation of a yarn whichcan be knitted in essentially dead 'or nonlively condition but haswithin it the potential ability to attain a lively or twisting statethereafter even when present in a fabric, and the preparationof a fabricfrom if such yarn and the production in such fabric of the lively stateof the yarn whereby the fabric contracts, and may exhibit a crepeeffect, and assumes a correlated condition of stretchability.

The examples are illustrative; and the invention can obviously bepracticed in many other ways in accordance with this disclosure and thescope of the claims.

I claim:

1. The method of making a stretchable fabric, which comprisespre-setting yarn of stretched microcrystallin'e polymer at an elevatedtemperature below the adhesive temperature of the material and withoutsignificant tension thereon whereby to fix therein a condition towardwhich it returns during a later less rigorous heat treatment, twistingthe yarn, twist-setting the yarn under conditions less rigorous thanthose of the pre-setting whereby a part of the strain produced in theyarn by the twisting is relieved and another part remains activetherein, removing twist from the twist-set yarn so that it attains anessentially dead and non-lively condition with a potential twisttherein, preparing a fabric from the yarn while in essentially deadcondition, and thereafter subjecting the fabric to an elevatedtemperature under conditions etfectivefor releasing a part of thepotential twist whereby the said yarn in the fabric becomes lively andthe fabric contracts.

2. The method of making a stretchable fabric from stretchedmicrocrystalline polyamide fiber yarn, which comprises subjecting theyarn to pre-setting under elevated temperature conditions below theadhesion temperature of the material whereby to fix therein a conditiontoward which it returns during a later less rigorous heat treatment,twisting the yarn, subjecting the twisted yarn to twist-setting at anelevated temperature which is not higher than 32 degrees F. below thepre setting temperature whereby a part of the strain produced in theyarn by the twisting is relieved and another part remains activetherein, removing twist from the twist-set yarn so that it attains anessentially dead and non-lively condition with a potential twisttherein, preparing a fabric from the yarn while in essentially deadcondition, and thereafter subjecting the fabric to an elevatedtemperature for releasing at least a part of the potential twist underelevated temperature conditions less rigorous than those ofthepre-setting whereby the said yarn in the fabric becomes lively andthe fabric contracts.

3. The method of making a stretchable fabric, which comprisespre-setting yarn of stretched microcrystalline polymer at an elevatedtemperature below the adhesive temperature of the material and withoutsignificant tension thereon and under humid conditions whereby to fixtherein a condition toward which it returns during a later less rigorousheat treatment, twisting the yarn, heating the twisted yarn under humidconditions at a lesser temperature whereby a part of the strain producedin the yarn by the twisting is relieved and another part remains activetherein, removing twist from the yarn so that it attains an essentiallydead and non-lively condition with a potential twist therein, preparinga fabric from the yarn while in such essentially dead condition, andthereafter subjecting the fabric to a third heat treatment under humidconditions for releasing a part of the potential twist whereby the saidyarn in the fabric becomes lively and the fabric contracts.

4. The method as in claim 3, in which the said third heating is at atemperature less than the temperature of the pre-setting treatment.

5. The method as in claim 3, in which the said third heating is at atemperature greater than the temperature of the twistetting treatment.

6. The method as in claim 3, in which the said third heating is at atemperature not greater than the temperature of the twistettingtreatment.

7. The method of treating a yarn of stretched microcrystalline polymer,which comprises heating the, same *nnder humid conditions to an elevatedtemperature below the adhesive temperature of the material whereby tofix therein a condition toward which it returns during 'a less rigorousheat treatment, twisting the yarn, and heating the twisted yarn underhumid conditions and at an elevated temperature below that of thepre-setting whereby a part of the strain produced in the yarn by thetwisting is relieved and another part remains active therein, andremoving twist from the twist-set yarn so that it attains an essentiallydead and non-lively condition with a potential twist therein.

8. A fabric made inaccordance with claim 1, and characterized in thatthe yarn thereof has residual potential twist therein.

9. A yarn made in accordance with the process of claim 7, andcharacterized in being in essentially dead and nonlively condition andhaving therein a potential twist which can be activated by subjection ofthe yarn to heating in a humid atmosphere.

10. The method of making a stretchable fabric, which comprisespre-setting at least two yarns of stretched microcrystaliine polymer atan elevated temperature below the adhesive temperature of the materialand without significant tension thereon whereby to fix in each thereof acondition toward which the yarn returns during a later less rigorousheat treatment, twisting the yarns independently in the same direction,twist-setting the yarns under conditions less rigorous than those of thepre-settings whereby a part of the twist produced strain in therespective yarn is relieved and another part remains efiective therein,plying the yarns with a plying twist in the opposite direction wherebythe composite yarn attains an essentially dead and non-lively conditionwith a potential twist therein, preparing a fab dead condition, andelevated temperature: ing a major part of" composite yarn in the,contracts.

11. The method independently pre-se the steps thereof, s in oppositedirections; said two yarns in d cessive bands of the. fabric is thensubjec 12. The method tion is by knitting, in the knit goods.

References UNIT 2,290,253 Sc 2,564,245 2,641,914 Neum 2,662,558 Me2,772,191 Bur 297,810 s f O American H" 1952, Textile B H June 25, 1957J. w. SCHAPPEL ETAL 2,796,656 MODIFIED REGENERATEO CELLULOSE ARTICLESAND METHOD FOR MAKING THE SAME Filed Sept. 6, 1952 VISCOSE SPINNINGSOLUTION ADDITIVE MIXTURE OF POLYACRYLAMIDE-FORMALDEHYDE PRECONDENSATETHICKENER SPINNING AND STRETCHING' WET PROCESSING CURE IN PRESENCE OFCROSS- LINKING CATALYST

